Pressure relieving devices comprising rupture discs and holders are known. They are usually fitted as prefabricated units in pipelines, vessels, reaction apparatus, and similar technical hollow bodies for protection against unacceptable pressure changes. The prefabrication of the pressure-relieving devices facilitates and speeds up their exchange in lines and apparatus and, in addition, ensures that the sensitive rupture discs do not suffer any damage due to improper handling, for example when being inserted into the holder.
It is also known to assist the tearing open of the rupture disc by the use of a tearing spike or a group of cutters. To ensure reliable bursting of the disc, the tearing device is located in the region of the disc center. A precise reaction to the given response pressure is achieved by changing the distance between the tearing spike or cutter edges and the plane of the disc. In a practical embodiment, the tearing device is set on a threaded rod. By variation of the distance between the spike or cutter edge and plane of the rupture disc, it is also possible to modify the pressure relieving device so it responds to other pressures without the necessity of changing the rupture disc. Finally, for special applications, the group of cutters can be arranged, not only on one side of the rupture disc, but on both sides, so that the pressure-relieving device is effective in both directions.
A disadvantage of the known pressure-relieving devices described above is that the hollow body surface area closed by the rupture disc is not cleared instantaneously around its entire circumference, even if a tearing device is used. If, for example, four cutter edges arranged in the form of a cross are used, the rupture disc is cut open segmentally. In particular in applications in which relief must take place at relatively low pressures, the complete tearing open of the rupture disc may be delayed in time and the unhindered flow of the medium leaving or entering may be impaired. In addition, the prior art mounting of the tearing device on a threaded rod is not always satisfactory, because the device is difficult to handle.